Spraying process for insulating coating of square battery

Abstract

The present invention relates to the technical field of square battery preparation. To solve the problems of high film application defect rate and low film application efficiency when using an insulating film to improve the insulation of the outer shell of a square battery in the prior art, a spraying process for an insulating coating of a square battery is disclosed, which includes the following steps: (1) performing surface cleaning on the outer shell of the square battery; (2) spraying the coating material onto the surface of the dried outer shell and then cooling the outer shell. The present invention uses a spraying method to coat an insulating layer on the surface of the outer shell of the square battery. The insulating layer can wrap the outer shell and make the surface of the square battery flat without wrinkles, and will not affect the assembly of the square battery into a battery pack. The insulating layer material has a good bonding effect with the outer shell and is resistant to high temperature and corrosion, and can provide long-term insulation protection for the square battery, thereby improving the safety performance of the battery. After adopting the process of the present invention, there is no need to wrap a blue film around the square battery anymore, and the production efficiency is high and the product defect rate is low.

Description

Technical Field

[0001] The present invention relates to the technical field of square battery preparation, and particularly to a spraying process for an insulating coating of a square battery. Background Art

[0002] During the production process of square batteries, an insulating layer is adhered to the battery surface to protect the finished batteries. The insulating layer not only prevents battery short - circuit, but also prevents the electrochemical corrosion during the processing from affecting the isolation effect of the housing. Blue film coating is an important process in the battery production process. However, in the actual film - coating process, due to the uneven surface of the battery housing and the relatively wide blue film, problems such as blue film wrinkling and bubbling often occur during the film - sticking process. At the same time, blue film overlap is likely to occur at the edges and corners of the battery, and the adhesion area is small, making it difficult to ensure the bonding strength. After the battery is stored for a period of time, the blue film will come off, affecting the assembly of the battery pack.

[0003] For example, in the "Insulating Film Structure of a Square Battery and Square Battery" disclosed in the Chinese patent literature, with the publication number CN215527812U, the insulating film structure of the square battery includes a top wall, two first side walls and two second side walls. An avoidance hole is provided on the top wall, and the top wall is configured to fit with the top surface of the battery body. The two first side walls are both connected to the top wall, and the two first side walls respectively correspond to and cover the front side and the rear side of the battery body; the two second side walls are both connected to the top wall, and the two second side walls can respectively cover part of the left side surface and part of the right side surface of the battery body. Although the use of an insulating film to coat the square battery in this patent reduces the coating operation through structural design, it cannot solve problems such as film - sticking wrinkles and bubbles. Therefore, the bonding strength and protection time of the insulating film need to be improved. Summary of the Invention

[0004] In order to overcome the problems of high film - sticking defect rate and low film - sticking efficiency when using an insulating film to improve the insulation of the square battery housing in the prior art, the present invention provides a spraying process for an insulating coating of a square battery. This process can provide a high - temperature - resistant and corrosion - resistant insulating coating on the surface of the square battery housing. The insulating coating can provide long - term insulation protection for the square battery housing, and the process operation is simple and does not affect the assembly of the battery into a battery pack.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A spraying process for an insulating coating of a square battery includes the following steps:

[0007] (1) Clean the surface of the housing of the square battery;

[0008] (2) Spray the coating material onto the surface of the dried housing, and then cool the housing.

[0009] In the present invention, the coating material is melted and then sprayed onto the surface of the battery case to form an insulating protective layer with controllable thickness and good consistency. Moreover, the edges and corners of the battery case can also be evenly coated by the insulating protective layer, and the bonding effect between the insulating protective layer and the battery case is good. The present invention can replace the blue film coating process. Compared with the blue film coating, the preparation efficiency of the present invention is high and the defective rate is low.

[0010] Preferably, in the step (1), the cleaning method for the surface of the case is laser cleaning or plasma cleaning.

[0011] To improve the bonding strength of the coating on the surface of the case, impurities attached to the surface of the case, such as dust and grease, need to be removed completely. Laser cleaning and plasma cleaning have good cleaning effects on the case, can activate the aluminum case and form a dense oxide layer. At the same time, laser cleaning and plasma cleaning are dry cleaning methods and do not require a drying step, which improves the processing efficiency and avoids recontamination of the case.

[0012] Preferably, the coating material in the step (2) comprises the following components in parts by weight: 80-90 parts of PET, 10-15 parts of bisphenol A epoxy resin, 3-8 parts of sodium poly(ethylene-co-methacrylic acid), 5-10 parts of nano-fillers, and 0-3 parts of pigments.

[0013] The coating material is based on ethylene terephthalate (PET) material. PET has good insulation, strong corrosion resistance, low cost, and the viscosity of molten PET is 100 Pa·S, which is suitable for spraying. Sodium poly(ethylene-co-methacrylic acid) is used as a nucleating agent, which can improve the crystallinity of PET, reduce the melting temperature, and improve the toughness and wear resistance of PET. However, too much addition of sodium poly(ethylene-co-methacrylic acid) will cause an increase in the viscosity of PET, which is not conducive to the spraying effect. Bisphenol A epoxy resin has good corrosion resistance, mechanical properties, and insulation, and can improve the adhesion ability of the coating material to the battery case. Nano-fillers are used to improve the mechanical properties and thermal conductivity of the coating material. Pigments can also be added to the coating material to facilitate the observation and inspection of the coating quality.

[0014] Preferably, in the step (2), the nano-fillers are boehmite or alumina.

[0015] Preferably, in the step (2), the particle size of the nano-fillers is 30-100 nm.

[0016] Preferably, the coating material in the step (2) is prepared by the following steps:

[0017] A. After stirring and mixing PET, bisphenol A epoxy resin and sodium poly(ethylene-co-methacrylic acid), then add the remaining components and mix to obtain a mixture;

[0018] B. Melt and blend the mixture. After melting and blending the mixture, it is ready for spraying.

[0019] Preferably, in step B, the melting temperature is 220 - 270 °C.

[0020] Preferably, in the spraying operation of step (2), the air pressure parameter is 6 - 8 MPa, and the distance between the nozzle and the surface of the housing is controlled within 5 - 7 cm.

[0021] Within the above parameter range, the bonding between the coating and the outer shell is firm, and the spraying is uniform.

[0022] Preferably, the spraying operation in step (2) is the screw spraying method.

[0023] Preferably, the thickness of the insulating coating in step (2) is not less than 50 μm.

[0024] When the thickness is too small, the insulation protection effect is not good; however, if the thickness of the insulating coating is too thick, it will also affect the installation of the battery pack and the heat dissipation of the battery.

[0025] Therefore, the present invention uses spraying to coat an insulating layer on the surface of the square battery housing. This insulating layer can wrap the outer shell and make the surface of the square battery flat without wrinkles, and will not affect the assembly of the square battery into a battery pack. The bonding effect between the insulating layer material and the outer shell is good, and it is resistant to high temperature and corrosion, which can provide long-term insulation protection for the square battery, thereby improving the safety performance of the battery. After adopting the process of the present invention, there is no need to cover the square battery with a blue film anymore, which fundamentally solves the problems in the process of pasting the blue film. At the same time, the process of the present invention has high production efficiency and low product defect rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic flow chart of the process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following further describes the present invention in conjunction with the drawings and specific implementation methods.

[0028] Example 1

[0029] A spraying process for an insulating coating of a square battery, as Figure 1 shown, includes the following steps:

[0030] (1) Perform plasma cleaning on the outer shell of the square battery;

[0031] (2) Add 90 parts of PET, 15 parts of bisphenol A epoxy resin, and 8 parts of sodium poly(ethylene - co - methacrylate) to a high - speed mixer in sequence, stir and mix evenly, then add 10 parts of alumina with a particle size of 50 nm and 2 parts of blue dye, stir and mix to obtain a mixture, and melt and blend the mixture to obtain a coating material;

[0032] (3) After the coating material is conveyed by a screw, it is sprayed onto the surface of the outer shell. The spraying pressure is 7 MPa, the distance between the nozzle and the outer shell is 5 cm. Then the outer shell is cooled, and the appearance of the coating on the surface of the outer shell after spraying is inspected, and it is detected whether the coating thickness is 50 μm.

[0033] Example 2

[0034] A spraying process for the insulating coating of a square battery, which is different from Example 1 in that the coating thickness is 80 μm.

[0035] Example 3

[0036] A spraying process for the insulating coating of a square battery, which is different from Example 1 in that the formulation of the coating material is 80 parts of PET, 15 parts of bisphenol A epoxy resin, 3 parts of sodium poly(ethylene-co-methacrylic acid), 5 parts of boehmite with a particle size of 30 nm, and 2 parts of

[0037] blue dye.

[0038] Comparative Example 1

[0039] A spraying process for the insulating coating of a square battery, which is different from Example 1 in that the formulation of the coating material is 90 parts of PET, 8 parts of sodium poly(ethylene-co-methacrylic acid), 10 parts of alumina with a particle size of 50 nm, and 2 parts of blue dye.

[0040] Comparative Example 2

[0041] A spraying process for the insulating coating of a square battery, which is different from Example 1 in that the formulation of the coating material is 80 parts of PET, 15 parts of bisphenol A epoxy resin, 10 parts of alumina with a particle size of 50 nm, and 2 parts of blue dye.

[0042] Comparative Example 3

[0043] A spraying process for the insulating coating of a square battery, which is different from Example 1 in that the formulation of the coating material is 80 parts of PET, 15 parts of bisphenol A epoxy resin, 20 parts of sodium poly(ethylene-co-methacrylic acid), 10 parts of alumina with a particle size of 50 nm, and 2 parts of blue dye.

[0044] The square battery outer shells prepared in the above examples and comparative examples are cut into specimens of 5 mm * 30 mm, and a tensile machine is used to clamp the specimens and the coating for peel strength testing. Then, the square battery outer shells prepared in the above examples and comparative examples are assembled into square batteries, and the insulation impedance between the battery positive electrode and the outer shell and the voltage withstand test between the positive electrode and the outer shell are carried out on the batteries. The results are shown in the following table.

[0045] Item Adhesion force (N / 5mm) Internal resistance (GΩ) Withstand voltage (V) Example 1 10.2 3.0 2000 Example 2 11.0 2.4 2000 Example 3 11.5 4.5 2000 Comparative Example 1 9.5 2.0 2000 Comparative Example 2 8.5 2.1 2000 Comparative Example 3 8.4 1.9 2000

[0046] As can be seen from the data in the above table, the insulating coating described in the present invention can improve the insulation performance of the square battery case, and has a good bonding effect with the square battery case, and is not easy to fall off.

[0047] Comparing Example 1 and Comparative Example 1, it can be seen that when the epoxy resin is missing in the coating material, both the insulation performance and the adhesion of the insulating coating decrease; when poly(ethylene-co-methacrylic acid) sodium salt is not used or the addition amount of poly(ethylene-co-methacrylic acid) sodium salt is too much, the performance of the coating material will also decrease. Therefore, the adhesion and internal resistance of Comparative Example 2 and Comparative Example 3 are less than those of Example 1.

Claims

1. A spraying process for the insulating coating of a square battery, characterized in that, It includes the following steps: (1) Surface-clean the outer shell of the square battery; (2) Spray the coating material onto the surface of the dried outer shell, and then cool the outer shell; the coating material includes the following components in parts by weight: 80-90 parts of PET, 10-15 parts of bisphenol A epoxy resin, 3-8 parts of sodium poly(ethylene-co-methylacrylate), 5-10 parts of nano-fillers, and 0-3 parts of pigments.

2. The spraying process of a square battery insulation coating according to claim 1, characterized in that, In step (1), the method for cleaning the surface of the outer shell is laser cleaning or plasma cleaning.

3. The spraying process of a square battery insulation coating according to claim 1, characterized in that, In step (2), the nano-filler is boehmite or alumina.

4. The spraying process of an insulating coating for a square battery according to claim 3, characterized in that, In step (2), the particle size of the nano-filler is 30-100 nm.

5. The spraying process of a square battery insulation coating according to claim 1, characterized in that, The coating material in step (2) is prepared by the following steps: A. Stir and mix PET, bisphenol A epoxy resin and sodium poly(ethylene-co-methylacrylate), and then add the remaining components to mix to obtain a mixture; B. Melt and blend the mixture and wait for spraying.

6. The spraying process of a square battery insulation coating according to claim 5, characterized in that, The melting temperature in Step B is 220 - 270 o °C.

7. A spraying process for an insulating coating of a square battery according to claim 1, characterized in that, In the spraying operation of step (2), the air pressure parameter is 6-8 MPa, and the distance between the nozzle and the surface of the shell is controlled at 5-7 cm.

8. The spraying process of an insulating coating for a square battery according to claim 1 or 7, characterized in that, The spraying operation in step (2) is the screw spraying method.

9. The spraying process of a square battery insulation coating according to claim 1, characterized in that, In step (2), the thickness of the insulating coating is not less than 50 μm.

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